The 104 monoclonal antibody reacts with the mouse CD45 molecule, the leukocyte common antigen (LCA) in CD45.2-expressing mouse strains. The strains that express CD45.2 include the most commonly used mouse strains C57BL/6, BALB/c, C58, DBA/1, DBA/2, C3H/He, CBA, 129, A and AKR. CD45.2 is expressed by all leukocytes in these strains.